Tensioner for a power transmission belt and method of making the same

ABSTRACT

A tensioner for a power transmission belt that is adapted to be operated in an endless path and a method of making the tensioner is provided, the tensioner comprising a support unit for being fixed relative to the belt, a belt engaging unit carried by the support unit and being movable relative thereto, a coiled torsion spring having a first end operatively interconnected to the support unit and a second end operatively interconnected to the belt engaging unit for urging the belt engaging unit relative to the support unit and against the belt with a force to tension the belt, the spring having a certain torque when the belt engaging unit is disposed at a certain position relative to the support unit, the tensioner having changeable structure holding one of the ends in an adjusted position relative to its respective operatively interconnected unit so as to provide for the certain torque of the spring when the belt engaging unit is disposed at the certain position relative to the support unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of its copendingparent patent application Ser. No. 867,259, filed Apr. 10, 1992, nowU.S. Pat. No. 5,169,368, which, in turn, is a divisional patentapplication of its copending parent patent application Ser. No. 771,291filed Oct. 4, 1991, now U.S. Pat. No. 5,129,864, which, in turn, is adivisional patent application of its copending parent patentapplication, Ser. No. 661,141, filed Feb. 27, 1991, now U.S. Pat. No.5,083,984.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new tensioner for a power transmission beltthat is adapted to be operated in an endless path and to a new method ofmaking such a tensioner.

2. Prior Art Statement

It is known to provide a tensioner for a power transmission belt that isadapted to be operated in an endless path, the tensioner comprising asupport means for being fixed relative to the belt, a belt engagingmeans carried by the support means and being movable relative thereto, acoiled torsion spring having a first end operatively interconnected tothe support means and a second end operatively interconnected to thebelt engaging means for urging the belt engaging means relative to thesupport means and against the belt with a force to tension the belt, thespring having a certain torque when the belt engaging means is disposedat a certain position relative to the support means. For example, seethe U.S. Pat. No. 4,596,538, to Henderson.

SUMMARY OF THE INVENTION

It is one of the features of this invention to provide a new belttensioner that has unique means for adjusting the torque of the torsionspring thereof to a desired torque when the belt engaging means thereofis disposed at a certain position relative to the support means thereof.

In particular, it was found according to the teachings of this inventionthat the tensioner can be provided with changeable structure for holdingone of the ends of the spring in an adjusted position relative to itsrespective operatively interconnected part of the tensioner so as toprovide for a certain torque of the spring when the belt engaging meansis disposed at a certain position relative to the support means.

For example, one embodiment of this invention comprises a tensioner fora power transmission belt that is adapted to be operated in an endlesspath, the tensioner comprising a support means for being fixed relativeto the belt, a belt engaging means carried by the support means andbeing movable relative thereto, a coiled torsion spring having a firstend operatively interconnected to the support means and a second endoperatively interconnected to the belt engaging means for urging thebelt engaging means relative to the support means and against the beltwith a force to tension the belt, the spring having a certain torquewhen the belt engaging means is disposed at a certain position relativeto the support means, the tensioner having changeable structure holdingone of the ends in an adjusted position relative to its respectiveoperatively interconnected means so as to provide for the certain torqueof the spring when the belt engaging means is disposed at the certainposition relative to the support means.

Accordingly, it is an object of this invention to provide a newtensioner for a power transmission belt that is adapted to be operatedin an endless path, the tensioner of this invention having one or moreof the novel features of this invention as set forth above orhereinafter shown or described.

Another object of this invention is to provide a new method for making atensioner for a power transmission belt that is adapted to be operatedin an endless path, the method of this invention having one or more ofthe novel features of this invention as set forth above or hereinaftershown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary front view of the belt tensioner of thisinvention mounted to a support bracket and illustrating in full linesone position thereof and in phantom lines other positions thereof.

FIG. 2 is a fragmentary cross-sectional view taken on line 2--2 of FIG.1;

FIG. 3 is an exploded perspective view of the various parts of thetensioner of FIGS. 1 and 2.

FIG. 4 is an exploded perspective view illustrating various parts forsetting the torque of the spring of the tensioner of this inventionduring the method of making the tensioner according to the method ofthis invention.

FIG. 5 is a view similar to FIG. 4 illustrating certain of the parts intheir assembled relation.

FIG. 6 is a side view of the parts illustrated in FIG. 5 with part ofthe structure being taken on line 6--6 of FIG. 5.

FIG. 7 is a view similar to FIG. 6 and illustrates the method of thisinvention for locking the tensioner in the adjusted position thereof.

FIG. 8 is an exploded perspective view illustrating another embodimentof the tensioner of this invention.

FIG. 9 is a side view of the parts of FIG. 8 in a certain assembledrelation thereof.

FIG. 10 is a view similar to FIG. 9 and illustrates the parts in theirlocked position.

FIG. 11 is a view similar to FIG. 1 and illustrates another tensioner ofthis invention.

FIG. 12 is a fragmentary cross-sectional view taken on line 12--12 ofFIG. 11.

FIG. 13 is an exploded perspective view of the various parts that formthe tensioner of FIGS. 11 and 12.

FIG. 14 is an exploded perspective view of certain of the parts of thetensioner of FIGS. 11 and 12 and illustrates one of the steps of themethod of this invention for making the tensioner of FIGS. 11 and 12.

FIG. 15 is a perspective view of the parts of FIG. 14 in the assembledrelation thereof.

FIG. 16 is an enlarged fragmentary view of part of the assembledstructure illustrated in FIG. 15.

FIG. 17 is a view similar to FIG. 16 and illustrates the one end of thespring being disposed in an adjusted position thereof and illustratingthe locking spacers therefor in an exploded manner.

FIG. 18 is a view similar to FIG. 17 and illustrates the spacers of FIG.17 in their inserted and final locking positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the various features of this invention are hereinafter illustratedand described as being particularly adapted to provide a tensioner for acertain type of power transmission belt, it is to be understood that thevarious features of this invention can be utilized singly or in variouscombinations thereof to provide a tensioner for other types of belts asdesired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings because the drawings are merely utilized toillustrate one of a wide variety of uses of this invention.

Referring now to FIGS. 1 and 2, the new belt tensioner of this inventionis generally indicated by the reference numeral 20 and is illustrated asbeing interconnected to a support bracket 21 of an internal combustionengine (not shown) by a single bolt means 22 in a manner fully set forthin the aforementioned U.S. Pat. No. 4,661,087, to Henderson, wherebythis patent is being incorporated into this disclosure by this referencethereto. Of course, other mounting means can be used.

The tensioner 20 comprises a support means 23 that comprises acup-shaped casing 24, a shaft means 25 and a plate means 26 allinterconnected together so that when the support means 23 isinterconnected to the support bracket 21, the support means 23 remainsstationary with the support bracket 21 as is well known in the art.

The tensioner 20 also comprises a belt engaging means 27 that comprisesan arm 28 that is provided with a tubular arbor 29 that is rotatablydisposed on the shaft means 25 so as to pivotally mount the beltengaging arm 28 to the shaft means 25, the belt engaging means 27further comprising a pulley means 30 that is rotatably mounted to an end31 of the belt engaging arm 28 so that an outer peripheral surface 32 ofthe pulley 30 can engage against a power transmission belt that isadapted to be operated in an endless path relative to the supportbracket 21. Such a belt construction 33 is illustrated in phantom linesin FIG. 1.

The tubular arbor 29 of the belt engaging means 27 of this invention isa part that is initially separate from the belt engaging arm 28 but issubsequently secured thereto by a locking ring 34 in a mannerhereinafter set forth so that the arbor 29 and arm 28 will rotate inunison whereas the arbor of the belt tensioner set forth in theaforementioned U.S. Pat. No. 4,661,087, to Henderson, is integral andone-piece with the belt engaging arm.

The tensioner 20 also comprises a coiled torsion spring 35 formed from aflat metallic ribbon coiled upon itself so as to have an inner end 36and an outer end 37. Also an antifriction ribbon 38 is interleavedbetween the coils of the spring 35 to reduce friction of such coilsduring the winding and unwinding thereof in a manner well known in theart. The spring 35 is disposed in the cup-shaped casing 24 with theouter end 37 of the spring 35 extending through a slot 39 in thecup-shaped casing 24 and hooking against a surface 40 thereof so as tointerconnect the end 37 of the spring 35 to the support means 23. Theinner end 36 of the spring 35 is tang-like and is received in a slot 41,FIG. 4, of the arbor 29 of the belt engaging means 27 so as tointerconnect the spring 35 to the belt engaging means 27.

When the tensioner 20 is assembled in a manner hereinafter set forth,the torsion spring 35 has been so wound that the same tends to move thebelt engaging arm 28 in a clockwise direction in FIG. 1 from the phantomline position indicated by the reference numeral 42 in FIG. 1 to thephantom line position represented by the reference numeral 43 in FIG. 1so that the pulley 30 will engage against the belt 33 at the positionindicated by the solid line to impose a tensioning force on the belt 33in a manner well known in the art.

In the past, each spring 35 was so constructed and arranged that whenthe same was assembled in a tensioner the same was to provide a certaintorque on the belt engaging means when the belt engaging arm wasdisposed at a certain position relative to the support means andtherefore would provide for proper tensioning of a belt during the usethereof. However, it was found according to the teachings of thisinvention that inconsistent spring torque makes keeping tensioner torqueoutput within the required tolerances for each different type of engineuse very difficult whereby spring sorting by torque output and selectiveassembly of the tensioners are costly and produce high spring scraprates.

Therefore, it was found according to the teachings of this inventionthat the tensioner 20 can be provided with changeable structure thatholds one of the ends of the spring in an adjusted position relative toits respective operatively interconnected means so as to provide for acertain torque of the spring when the belt engaging means is disposed ata certain position thereof relative to the support means and in theembodiment of the tensioner 20 of this invention illustrated in FIGS.1-7, such changeable structure is provided by the arbor 29 of the beltengaging means 27 initially being separate from the belt engaging arm 28in a manner hereinafter set forth.

In order to provide antifriction material on each side of the torsionspring 35 when the same is disposed in the cup-shaped casing 23 in theassembled relation therewith, a pair of disc-like members 44 and 45 areprovided and are disposed on opposite sides of the spring 35, thedisc-like member 44 having a tubular bearing structure 46 that isdisposed between the shaft means 25 and the inner peripheral surface 47of the arbor 29 of the belt engaging means 27 so as to provide frictionmaterial between the shaft means 25 and the pivoting movement of the arm28 in a manner well known in the art. The disc-like member 45 has apartial tubular structure 48 that is disposed adjacent the inner coil49' of the spring 35 for the reasons fully set forth in theaforementioned U.S. Pat. No. 4,596,538, to Henderson, whereby a furtherdiscussion of the disc-like members 44 and 45 is deemed unnecessary asthe details of the members 44 and 45 are fully disclosed in such patent.

Additionally, a disc-like member 49 of polymeric material is disposedbetween the end plate 26 and the side 50 of the belt engaging arm 28 toreduce friction between the pivoting movement of the arm 28 and thestationary end plate 26.

Thus, since the details of the structure and the operation of the belttensioner 20 are similar to the belt tensioner fully disclosed in theaforementioned patent to Henderson, U.S. Pat. No. 4,661,087, a furtherdiscussion of the structure and operation of the belt tensioner 20 ofthis invention is deemed unnecessary.

Therefore, the aforementioned feature of this invention for adjustingthe torque of the spring 35 during the assembly of the tensioner 20 willnow be described in detail.

The arm 28 of the tensioner 20 is formed of metallic material and has astepped opening 51 passing therethrough and defining a first cylindricalsurface 52 and a second cylindrical surface 53 respectively adjacent theopposed sides 54 and 50 of the arm 28 while defining a flat internalannular shoulder 55 therebetween as illustrated in FIG. 3.

The arbor 29 is formed of metallic material and has a stepped externalperipheral surface defined by a first external cylindrical surface 56and a second external cylindrical surface 57 that has a smaller diameterthan the surface 56 and being separated therefrom by an outwardlydirected annular rib means 58 that is adapted to have its outerperipheral surface 59 substantially mate with the cylindrical surface 52of the arm 28 when the same is disposed therein and have a flat annularshoulder 60 engage against the annular shoulder 55 of the arm 28 in themanner illustrated in FIG. 2 whereby the peripheral surface 57 of thearbor 29 is disposed spaced radially inwardly from the internalperipheral surface 53 of the arm 28.

When the arbor 29 is first assembled in the opening 51 of the arm 28 inthe above manner, the arbor 29 can be rotated relative to the arm 28 andcan be subsequently locked in a desired rotational position thereof byhaving the knurled metallic ring 34, which has knurls 61 on the outerperipheral surface thereof and knurls 62 on the inner peripheral surfacethereof, inserted between the surfaces 53 and 57 of the arm 28 and arbor29 so that the knurls 61 and 62 thereof grip in a manner well known inthe press-fit art the respective surfaces 53 and 57 to lock the arbor 29to the arm 28 in such rotational position thereof so that thereafter thearm 28 and arbor 29 rotate in unison in that selected rotationalposition of the arbor 29 relative to the arm 28.

The arbor 29 has an end surface 63 provided with a plurality of openings64 disposed therein to cooperate with a plurality of projections 65 on arotatable tool 66 of an apparatus of this invention that is generallyindicated by the reference numeral 67 in the drawings.

The apparatus 67 includes a support structure that is generallyindicated by the reference numeral 68 in FIG. 6 and represented bydashed lines, the support structure 68 having an opening 69 passingtherethrough.

The arm 28 of a tensioner 20 is adapted to be disposed on the supportstructure 68 in the manner illustrated in FIG. 6 so that the opening 51thereof is aligned with the opening 69. The arm 28 is adapted to be heldon such structure 68 in a fixed manner by any suitable holding structure(not shown) so that the end 70 of the arm 28 will be located in a fixedposition on the support structure 68 for a purpose hereinafter setforth.

Thereafter, the arbor 29 is inserted into the opening 51 so that theshoulder 60 thereof abuts against the annular shoulder 55 of the arm 28.Thereafter, the disc member 45 is assembled over the arbor 29 and thenthe spring 35 is disposed over the arbor 29 and against the disc 45 withthe inner end 36 of the spring 35 being received in the notch 41 of thearbor 29.

The end 37 of the spring 35 is then moved to a set position that isrepresented by the reference numeral 71 in FIG. 5 by a holding pin 72 ofthe apparatus 67 so that the end 37 of the spring 35 is in the fixedposition 71 relative to the fixed position 73 for the end 70 of the beltengaging arm 28 in the manner illustrated in FIG. 5.

With the end 37 of the spring 35 held at the position 71 and the end 70of the arm 28 held at the position 73 as illustrated in FIG. 5, the tool66 is lowered against the arbor 28 so that the projections 65 arereceived in the openings 64 whereby the tool 66 can rotate the arbor 29in the direction indicated by the arrow 74 in FIG. 5 in the mannerillustrated in FIG. 6 to create a windup force of the spring 35 so thata desired output torque for the spring 35 will eventually be reached forthe settings 71 and 73 at which time the rotation of the tool 66 isterminated. While the tool 66 and thus the arbor 29 is being held inthat position, a ram 75 of the apparatus 67 is moved upwardly asrepresented by the arrow 76 in FIG. 6 to insert the locking ring 34through the opening 69 of the support means 68 and into the spacebetween the surfaces 53 and 57 of the arm 28 and the arbor 29 to lockthe arbor 29 in the set rotational position as being held by the tool 66as illustrated in FIG. 7.

Thereafter, the assembled arm 28, spring 35 and arbor 29 can be removedfrom the apparatus 67 as a completed subassembly by backing off the tool66 and the ram 75 whereby such subassembly can then be assembled withthe other parts of the tensioner 20 to complete the same in the mannerfully set forth in the aforementioned U.S. Pat. No. 4,596,538 toHenderson, and the torque of the spring 35 will be at an adjustedsetting thereof that will assure that when the belt engaging arm 28 isdisposed in a certain position relative to the support means 23, thespring 35 will provide a desired torque for tensioning a belt when thetensioner 20 is utilized in the manner illustrated in FIG. 1.

In this manner, it can be seen that the springs 35 for the tensioners 20of this invention need not be substantially identical to each other whenforming the tensioners 20 of this invention because the apparatus 67will assure that when each spring 35 is in the assembled relationillustrated in FIG. 4 wherein the end 37 of the spring 35 is at theposition 71 and the end 70 of the arm 28 is held at the position 73, thetool 66 can adjust the inner end 36 of the spring 35 to a certainposition that will provide a desired specified torque at which time thearbor 29 is then locked in place in such rotational position provided bythe tool 66.

While the locking ring 34 is utilized to lock the arbor 29 in thedesired rotational position in the opening 51 of the arm 28 in themanner previously set forth, it is to be understood that other lockingarrangements can be utilized.

For example, the surface 57 of the arbor 29 could itself be knurled sothat when the same is fully inserted into the arm 28, such knurls willlock with the surface 53 in the arm 28.

In particular, another tensioner of this invention is generallyindicated by the reference numeral 20A in FIGS. 8-10 and parts thereofsimilar to the tensioner 20 previously described are indicated by likereference numerals followed by the reference letter "A".

As illustrated in FIGS. 8-10, the arm 28A is identical to the arm 28previously described while the arbor 29A has the surface 57A thereofprovided with knurls 77 which will dig into the surface 53A of the arm28A when the arbor 29A is fully inserted down into the opening 51A ofthe arm 28A in the manner illustrated in FIG. 10 to lock the arbor 29Ain its rotational position relative to the arm 28A.

Thus, the apparatus 67A of this invention can be so constructed andarranged that initially the arm 28A will be held on the supportingstructure 68A with the end 70A thereof held in a certain position andthe arbor 29A will be held adjacent to the arm 28A by another supportingstructure 78 of the apparatus 67A so that the tool 66A could rotate thearbor 29A to a desired rotational position thereof that will provide thetorque output of the spring 35A when the outer end 37A of the spring 35Ais being held in a certain position relative to the end 70A of the arm28A in the manner previously set forth so that a ram 79 of the apparatus67A can then cooperate with the tool 66A to force the arm 28A and arbor29A together in the manner illustrated in FIG. 10 after the removal ofthe supporting structure 78 whereby the knurls 77 on the surface 57A ofthe arbor 29A will dig into the surface 53A of the arm 28A and therebylock the same together in the rotational position that will cause thetorque output of the spring 35A to be at the desired torque output inthe same manner as provided by the apparatus 67 when utilizing thelocking ring 34 previously set forth.

In order to ensure that the arbor 29A will lock in place, it may befound that the arbor 29A should be made out of a harder material thanthe arbor 29 so as to form stronger knurls 77 for the previouslydescribed locking function.

While the tensioners 20 and 20A previously described utilize arbors 29and 29A that are initially separate from the respective belt engagingarm 28 and 28A, it is to be understood that other changeable structurecan be utilized for changing the position of the inner end of the springin its interconnection to the arbor of the belt engaging arm so as toadjust the torque output of the spring for the reasons previously setforth.

In particular, another tensioner of this invention is generallyindicated by the reference numeral 20B in FIGS. 11-18 and parts thereofsimilar to the tensioners 20 and 20A previously described are indicatedby like reference numerals followed by the reference letter "B".

It can be seen from FIGS. 11-18 that the tensioner 20B is generallyidentical to the tensioner 20 previously described except that the arbor29B is integral and one-piece with the belt engaging arm 28B so that thearbor 29B cannot initially rotate relative to the arm 29B.

However, instead of the fixed arbor 29B having the narrow slot 41previously described for the arbor 29, the arbor 29B is provided with arelatively wide notch 80 in an outer peripheral surface 81 thereof thatdefines facing shoulders 82 and 83 as illustrated.

The apparatus 67B for assembling the spring 35B to the arm 28B is soarranged that the end 70B of the arm 28B is held at the position 73B asillustrated in FIG. 15 while the end 37B of the spring 35B is held atthe position 71B by the rod 72B of the apparatus 67B whereby the innerend 36B of the spring 35B will be located in the notch 80 of the arbor29B. Thereafter, the end 36B of the spring 35B is moved to a desiredposition within the notch 80 which will produce a certain torque output,such movement of the end 36B being by a tool similar to the tool 66 ofthe apparatus 67 except that the tool would only grasp the end 36B ofthe spring 35B and move the same to its desired torque output producingposition which would be as illustrated in FIG. 17. Thus, at least oneproperly sized arcuate spacer 84 and/or 85 can then be disposedrespectively into the notch 80 on opposite sides of the end 36B of thespring 35B and respectively engage against the edges 82 and 83 of thenotch 80 and the end 36B of the spring 35B to hold the end 36B of thespring 35B in the properly selected position thereof to provide thedesired output torque of the spring 35B while the end 37B of the spring35B is at the position 71B and the end 70B of the arm 28B is at theposition 73B.

Of course, for each different spring 35B, the end 36B thereof will be ata different position and different sizes of the spacers 84 and/or 85will be utilized to hold that end 36B at the desired position thereof.

In that manner, the operator of the apparatus 67B will be provided witha plurality of different spacers 84 and/or 85 wherein the sizes of thespacers 84 and/or 85 will be such that the same will hold the end 36B ofa spring 35B at a certain position within the notch 80 of the arbor 29Bof a belt engaging arm 28B.

Therefore, it can be seen that the tensioner 20B of this invention haschangeable structure holding one of the ends of the springs in anadjusted position relative to its respective operatively interconnectedmeans so as to provide for a certain torque of the spring when the beltengaging means is disposed at a certain position relative to the supportmeans.

While the various embodiments of the tensioner of this invention eachhave the inner end of the torsion spring adjusted by changeablestructure, it is to be understood that the other end of the spring couldbe changed by changeable structure during its interconnection with thesupport means, if desired. Additionally both ends of the spring could beprovided with changeable structure, if desired.

Therefore, it can be seen that this invention provides a new tensionerfor a power transmission belt that is adapted to be operated in anendless path and provides a new method of making such a tensioner.

While the forms and methods of this invention now preferred have beenillustrated and described as required by the Patent Statute, it is to beunderstood that other forms and method steps can be utilized and stillfall within the scope of the appended claims wherein each claim setsforth what is believed to be known in each claim prior to this inventionin the portion of each claim that is disposed before the terms "theimprovement" and sets forth what is believed to be new in each claimaccording to this invention in the portion of each claim that isdisposed after the terms "the improvement" whereby it is believed thateach claim sets forth a novel, useful and unobvious invention within thepurview of the Patent Statute.

What is claimed is:
 1. In a tensioner for a power transmission belt thatis adapted to be operated in an endless path, said tensioner comprisinga support means for be in fixed relative to said belt and having a shaftmeans, a belt engaging means carried by said support means and having amovable relative thereto, a coiled torsion spring having a first endoperatively interconnected to said support means and a second endoperatively interconnected to said belt engaging means for urging saidbelt engaging means relative to said support means and against said beltwith a force to tension support means and against said belt with a forceto tension said belt, said spring having a certain torque when said beltengaging means is disposed at a certain position relative to saidsupport means, the improvement wherein said tensioner has changeablestructure holding said second end of said spring in an adjusted positionrelative to said belt engaging means so as to provide for said certaintorque of said spring when said belt engaging means is disposed at saidcertain position relative to said support means.
 2. A tensioner as setforth in claim 1 wherein said changeable structure comprises a rotatablemember carried by said belt engaging means and comprising said arbormeans thereof.
 3. A tensioner as set forth in claim 2 wherein saidsecond end of said spring is tang-like, said rotatable member having aslot therein that receives said tang-like end of said spring therein soas to be interconnected to said second end of said spring.
 4. Atensioner as set forth in claim 2 wherein said rotatable member haslocking means locking said member in a certain rotational positionrelative to said belt engaging means to provide for said certain torque.5. A tensioner as set forth in claim 4 wherein said locking meanscomprises knurling means.
 6. A tensioner as set forth in claim 1 whereinsaid changeable means comprises a pair of spacers carried in spacedapart relation by said arbor means of said belt engaging means so as todefine a slot therebetween, said second end of said spring beingdisposed in said slot so as to be interconnected to said belt engagingmeans.
 7. A tensioner as set forth in claim 1 wherein said arbor meansof said belt engaging means has a notch therein that defined two spacedapart edge means, said changeable structure comprising a spacer disposedagainst one of said two edge means and said second end of said spring soas to be carried in said north.
 8. A tensioner as set forth in claim 1wherein said second end of said spring comprises an inner end thereof.9. A tensioner as set forth in claim 1 wherein said changeable structurecomprises removable spacer means disposed between said arbor means ofsaid belt engaging means and said second end of said spring.
 10. Atensioner as set forth in claim 1 wherein said changeable structurecomprises removable spacer means carried by said belt engaging means.11. In a method of making a tensioner for a power transmission belt thatis adapted to be operated in an endless path, said tensioner comprisinga support means for being fixed relative to said belt and having a shaftmeans, a belt engaging means carried by said support means and having anarbor means rotatably disposed on said shaft means and being movablerelative thereto, a coiled torsion spring having a first end operativelyinterconnected to said support means and a second end operativelyinterconnected to said belt engaging means for urging said belt engagingmeans relative to said support means and against said belt with a forceto tension said belt, said spring having a certain torque when said beltengaging means is disposed at a certain position relative to saidsupport means, the improvement comprising the step of forming saidtensioner to have changeable structure holding said second end of saidspring in an adjusted position relative to sad belt engaging means so asto provide for said certain torque of said spring when said beltengaging means is disposed at said certain position relative to saidsupport means.
 12. A method of making a tensioner as set forth in claim11 and including the step of forming said changeable structure tocomprise a rotatable member carried by said belt engaging means andcomprising said arbor means thereof.
 13. A method of making a tensioneras set forth in claim 12 and including the steps of forming said secondend of said spring to be tang-like, and forming said rotatable member tohave a slot therein that receives said tang-like end of said springtherein so as to be interconnected to said second end of said spring.14. A method of making a tensioner as set forth in claim 12 andincluding the step of forming said rotatable member to have lockingmeans locking said member in a certain rotational position relative tosaid belt engaging means to provide for said certain torque.
 15. Amethod of making a tensioner as set forth in claim 14 and including thestep of forming said locking means to comprise knurling means.
 16. Amethod of making a tensioner as set forth in claim 11 and including thesteps of forming said changeable means to comprise a pair of spacerscarried in spaced apart relation by said arbor means of said beltengaging means so as to define a slot therebetween, and disposing saidsecond end of said spring in said slot so as to be interconnected tosaid belt engaging means.
 17. A method of making a tensioner as setforth in claim 11 and including the steps of forming said arbor means ofsaid belt engaging means to have a notch therein that defines two spacedapart edge means, forming said changeable structure to comprise aspacer, and disposing said spacer against one of said two edge means andsaid second end of said spring so as to be carried in said notch.
 18. Amethod of making a tensioner as set forth in claim 11 and including thestep of forming said second end of said spring to comprise an inner endthereof.
 19. A method of making a tensioner as set forth in claim 11 andincluding the step of forming said changeable structure to compriseremovable spacer means disposed between said arbor means of said beltengaging means and said second end of said spring.
 20. A method ofmaking a tensioner as set forth in claim 11 and including the step offorming said changeable structure to comprise removable spacer meanscarried by said belt engaging means.